Apoptosis, or programmed cell death, is important for normal embryological/ananatomical development, host defense and suppression of oncogenesis. Faulty regulation of apoptosis has been implicated in cancer and many other human diseases which result from an imbalance between the process of cell division and cell death. Bcl-2 was originally identified at the chromosomal breakpoint of t(14;18)-bearing B-cell lymphomas and belongs to a growing family of proteins which regulate apoptosis. (Gross, A; McDonnell, J M; Korsmeyer, S. J. BCL-2 family members and the mitochondria in apoptosis. Genes & Development 1999, 13, 1899-1911, Cory, S.; Huang, D. C. S.; Adams, J. M. The Bcl-2 family: roles in cell survival and oncogenesis. Oncogene, 2003 22, 8590-8607. Danial, N. N.; Korsmeyer, S. J. Cell death: Critical control points. Cell 2004, 116, 205-218. Chao, D. T.; Korsmeyer, S. J. Bcl-2 family: regulators of cell death. Annu. Rev. Immunol. 1998, 16, 395-419). Apoptosis, Christopher Potten, James Wilson, Cambridge University Press, 2004). The Bcl-2 family of proteins include both anti-apoptotic molecules, such as Bcl-2 and Bcl-XL, and pro-apoptotic molecules, such as Bax, Bak, Bid and Bad. Bcl-2 contributes to cancer cell progression by preventing normal cell turnover caused by physiological cell-death mechanisms. Over-expression of Bcl-2 has been observed in 70% of breast cancer and many other forms of cancer (Buolaniwini, J. K. Novel anticancer drug discovery. Curr. Opin. Chem. Biol. 1999, 3, 500-509). The expression levels of Bcl-2 proteins also correlate with resistance to a wide spectrum of chemotherapeutic drugs and γ-radiation therapy (Reed, J. C.; Miyashita, T.; Takayama, S.; Wang, H.-G.; Sato, T.; Krajewski, S.; Aime-Sempe, C.; Bodrug, S.; Kitada, S.; Hanada, M. Bcl-2 family proteins: Regulators of cell-death involved in the pathogenesis of cancer and resistance to therapy. J. Cell. Biochem. 1996, 60, 23-32; Reed, J. C. Bcl-2 family proteins: strategies for overcoming chemoresistance in cancer. Advances in Pharmocology 1997, 41, 501-553; Strasser, A.; Huang, D. C. S.; Vaux, D. L. The role of the Bcl-2/ced-9 gene family in cancer and general implications of defects in cell death control for tumorigenesis and resistance to chemotherapy. Biochem. Biophys. Acta 1997, 1333, F151-F189; DiPaola, R. S.; Aisner, J. Overcoming Bcl-2- and p53-mediated resistance in prostate cancer. Semin. Oncol. 1999, 26, 112-116).
Members of the Bcl-2 family of proteins represent key regulators of apoptosis, with pro-apoptotic (e.g., Bax, Bak, Bid, Bim, Noxa, Puma) and anti-apoptotic function (e.g., Bcl-2, Bcl-xL, Mcl-1). Selective and competitive dimerization between pro- and anti-apoptotic members of the family determines the fate of a cell given pro-apoptotic stimulus. Although the precise roles of Bcl-2 and Bcl-xL in cancer are not completely understood, there are several lines of evidence that suggest that Bcl-2 and Bcl-xL not only contribute to cancer progression by preventing normal cell turnover, but also play a role in the resistance of cancer cells to current cancer treatments. Experimental over-expression of Bcl-2 (Bcl-xL) renders cancer cells resistant to a wide spectrum of chemotherapeutic agents and radiation (Bcl-2 family proteins: Regulators of cell-death involved in the pathogenesis of cancer and resistance to therapy. J. Cell. Biochem. 1996, 60, 23-32; Reed, J. C). Bcl-2 and/or Bcl-xL are over-expressed in more than 50% of all tumors as shown below (from Wang, S.; Yang, D.; Lippman, M. E. Targeting Bcl-2 and Bcl-xL with nonpeptidic small-molecule antagonists. Seminars in Oncology, 2003, 5, 133-142).
Bcl-2 over-Bcl-xL over-Cancer typeexpression (%)expression (%)Prostate20-40100 - hormone resistant 80-100—Breast60-8040-60Non-small cell lung20-40—Small cell lung60-80—Colorectal 50-10083Melanoma6590Multiple myeloma (at relapse)—77Head and Neck1352-75Pancreatic2390Hepatocellular carcinoma—80
Biological approaches to modulating Bcl-2 function using anti-sense oligonucleotides or single-chain antibodies have been shown to enhance tumor cell chemosensitivity (Ziegler, A.; Luedke, G. H.; Fabbro, D.; Altmann, K. H.; Stahel, R. A.; Zangemeister-Wittke, U. Induction of apoptosis in small-cell lung cancer cells by an antisense oligodeoxynucleotide targeting the Bcl-2 coding sequence. J. Natl. Cancer. Inst. 1997, 89, 1027-1036; Webb, A.; Cunningham, D.; Cotter, F.; Clarke, P. A.; Di Stefano, F.; Ross, P.; Corpo, M.; Dziewanowska, Z. Bcl-2 antisense therapy in patients with non-hodgkin lymphoma. Lancet 1997, 349, 1137-1141; Cotter, F. E. Phase I clinical and pharmacokinetic study of Bcl-2 antisense oligonucleotide therapy in patients with non-hodgkin's lymphoma. J. Clin. Oncol. 2000, 18, 1812-1823; Piche, A.; Grim, J.; Rancourt, C.; Gomez-Navarro, J.; Reed, J. C.; Curiel, D. T. Modulation of Bcl-2 protein levels by an intracellular anti-Bcl-2 single-chain antibody increases drug-induced cytotoxicity in the breast cancer cell line MCF-7. Cancer Res. 1998, 58, 2134-2140).
It has been shown that an anti-sense oligonucleotide (G3139) (Raynaud, F. I.; Orr, R. M.; Goddard, P. M.; Lacey, H. A.; Lancashire, H.; Judson, I. R.; Beck, T.; Bryan, B.; Cotter, F. E. Pharmacokinetics of G3139, a phosphorothioate oligodeoxynucleotide antisense to Bcl-2, after intravenous administration or continuous subcutaneous infusion to mice. J. Pharmacol. Exp. Ther. 1997, 281, 420-427), designed to hybridize to sequence in Bcl-2 mRNA, inhibits Bcl-2 expression, induces apoptosis and inhibits cell growth in human breast cancer cells having Bcl-2 over-expression (Chen, H. X., Marchall, J. L., Trocky, N., Baidas, S., Rizvi, N., Ling, Y., Bhagava, P., Lippman, M. E., Yang, D., and Hayes, D. F. A Phase I study of Bcl-2 antisense G3139 (Genta) and weekly docetaxel in patients with advanced breast cancer and other solid tumors. Proceedings of American Society of Clinical Oncology, 2000). Importantly, synergistic effects and complete tumor regression were observed in vivo in the combined treatments of G3139 with docetaxel. Therefore, Bcl-2 represents a highly attractive target for the development of a novel therapy for the treatment of many forms of cancers.
Limitations associated with the use of large molecules, such as oligonucleotides, proteins and polypeptides, as therapeutic agents include poor oral availability, poor in vivo stability, and high cost. More desirable therapeutics would be non-peptide, cell-permeable small molecules that bind to Bcl-2 and block the anti-apoptotic function in cancer and promote cell-death in tumors.
Various small molecules have been shown to inhibit the function of Bcl-2. For example, acyl sulfonamides were shown to inhibit the function of Bcl-2 and Bcl-xL in biochemical and in vitro assays. Nature (2005) 435, 677-681. Nevertheless, the need exists for additional small organic molecules that bind to Bcl-2 and block its anti-apoptotic function in cancer and promote cell death in tumors. The present invention fulfills this need and has other related advantages.